Land Mobile Satellite Research Articles

Study on the dual-orthogonal polarized MIMO wideband satellite mobile channel based on a 4-state LMS model

This paper focused on establishing a MIMO wideband land mobile satellite (LMS) channel statistics model. The particularity of this channel modeling was its wideband characteristics and the DPAs structure. Based on the Loo and Fontan model, a 4-state wideband LMS model was analyzed by combination of a Markov chain and properties of the wideband channel including its multipath excess delay and temporal-correlation performance. The paper also studied the effects of DPAs on channel modeling including the Cross Polarization Discrimination (XPD) and Cross Polarization Coupling (XPC). Through detailed analysis of the 4-state widebandLMSmodel and the effects of DPAs on channel modeling above, a typical dual-orthogonal polarized MIMO wideband satellite mobile channel model could be built. According to the modeling steps, channel time-series can be generated to assist further analysis of the system performance and evaluation of new technologies.

Packet scheduling in MIMO satellite long term evolution networks

Summary This paper deals with the performance evaluation of different packet scheduling schemes for Long Term Evolution mobile satellite systems based on the adoption of a multi-user MIMO technique. The major breakthrough of MIMO technology in terrestrial networks has motivated the interest here for the adoption of MIMO in mobile satellite systems as well. In particular, a land mobile dual-polarized GEO satellite system has been considered in this work. The aim of this paper is to propose new cross-layer packet scheduling schemes that achieve a good trade-off among throughput, QoS and fairness and to conduct performance comparisons with other scheduling schemes in the literature. This is the reason why this paper also proposes a new performance index that can be used to evaluate the overall performance of each scheduler. The work shows that the new cross-layer scheduler, called channel-based queue sensitive scheduler, attains the best performance in terms of the new comprehensive performance index, thus representing an interesting solution for future mobile satellite systems. Copyright © 2015 John Wiley & Sons, Ltd.

Performance evaluation of maximal ratio combining in Shadowed‐Rician fading land mobile satellite channels with estimated channel gains

The maximal ratio combining (MRC) scheme for Shadowed-Rician (SR) fading land mobile satellite (LMS) channels with estimated channel gains is studied, in this paper. It is assumed that satellite contains a single antenna and earth station (ES) has multiple antennas. For this set-up, a maximum-likelihood decoder is derived under assumption that perfect channel state information (CSI) is known; then the perfect CSI is replaced with estimated CSI in decision metric at ES. The MRC scheme for SR fading LMS channels has been studied in existing literature mostly with perfect CSI assumption. We derive approximate closed-form expressions of the probability density function, cumulative distribution, moment generating function (MGF), and analytical diversity order for the MRC based receiver in independent and identically distributed SR fading LMS channels with estimated channel gains. The author also provides approximate closed-form expressions of the outage probability and capacity of the considered scheme with estimated channel gains. Next, the author considers correlated SR fading LMS links and derive approximate bit error rate of the satellite system with estimated channel gains. It is shown from analysis and simulation that channel estimation error and correlation do not affect the diversity order but reduce the capacity of the considered system.

Estimation of carrier and channel parameters in time‐selective fading channels

Assuming a land-mobile satellite link with negligible multipath and shadowing effects, the corresponding channel model is adequately described by a correlated Rician distribution. In this context, the estimation of carrier and channel parameters has been investigated in some earlier work by means of an algorithmic approach primarily based on heuristic considerations. In the current study, the authors will review the results obtained so far from a maximum-likelihood (ML) point of view. A major output of the analysis is that the simple ad-hoc framework achieved previously is indeed an ML solution, when the impairments introduced by Rician fading are spectrally flat and strictly band limited.

Predictive relay-selection cooperative diversity in land mobile satellite systems

Cooperative diversity protocols promise a new dimension of diversity that provides better communication by engaging nearby relays in forming a ‘virtual’ array of antennas for combined signal transmission. The current incremental cooperative diversity algorithms incrementally select best relay(s) to cooperate based on the channel quality reported by the relays. However, the algorithms do not take into consideration the fact that the chosen best relay(s) at estimation may not always be the best at the time of communication. This is due to the time delay between the relay selection and its transmission of signal (problem of outdated channel quality information (CQI)). To solve this problem, the concept of channel prediction is introduced and employed whereby each relay determines a predicted value of its CQI based on its past measurements. The paper therefore develops a novel predictive relay-selection (PRS) cooperative diversity model that seeks to improve land mobile satellite communication through prediction protocols. In the model, the chosen best relay is the one with the best predicted CQI value instead of the traditional outdated one. Performance analysis of outage probability and average bit error probability for the newly developed PRS cooperation shows that the PRS cooperation is better than direct and outdated CQI relay communication. Copyright © 2015 John Wiley & Sons, Ltd.

Cooperative DVB-SH satellite broadcasting systems with rotated signal constellations

In this paper, we study the advantages of cooperation in broadcasting systems from a geosynchronous earth orbit (GEO) satellite to mobile terminals (MTs), achieved through a terrestrial complementary ground station (CGS) with fixed installment, which acts as a relay. Moreover and in the context of the digital video broadcasting-satellite- to-handheld (DVB-SH) standard, the performance improvements offered by the rotated constellations method are investigated, where prior transmission, a phase rotation of the transmitted symbols by a fixed angle is applied followed by a random component interleaver. Turbo codes with soft decision decoding and appropriate random channel interleavers are also considered. We present analytical expressions for the bit log-likelihood ratios (LLRs) that are needed for soft decision decoding at the MT turbo decoder, while the code combining technique is adapted to improve the end-to-end (E2E) performance. Then, we obtain through extensive computer simulations the average bit error probability (ABEP) of quadrature phase-shift keying (QPSK) signals received over pure land-mobile satellite (LMS) and pure CGS links for coding rates 1/3 and 6/7. Moreover, the optimal rotation angles are obtained for both links. E2E ABEP results are then presented assuming cooperation between GEO and CGS, while the power allocation issue is investigated under fixed total transmission power. Our performance evaluation results show that by using the constellation rotation technique, a performance gain can be achieved for high coding rates.

An Alternating Variable Step-Size Adaptive Long-Range Prediction of LMS Fading Signals

We propose a linear alternating variable step-size adaptive long-range prediction (AVSS-ALRP) scheme to predict fading signals which is especially suitable for a versatile two-state land mobile satellite (LMS) channel model at S-band. A three-step design procedure is presented to optimize the prediction performance. Firstly, we establish the Gilbert-Elliot channel model based on first-order Markov chain for satellite communication downlink and take advantage of smoothing average to obtain channel observed values. At a second stage, eigenvalue decomposition method is applied to predict future long-range channel state instead of weighted prediction. Finally, combining variable step-size least mean squares and adaptive long-range prediction, we introduce the VSS-ALRP algorithm to predict LMS channel fading signals in the case of “ good” state, and the obtained prediction results would be revised based on the linear prediction of error when shadowing condition is in the “ bad” state. Simulation results show that the proposed scheme can not only offer an accurate prediction for long-range channel state and fading signals over the two-state Gilbert-Elliot channel model and greatly enhance the fading signals’ autocorrelation, but also have considerably better performance than long-range prediction (LRP) algorithm from the results of mean square error (MSE) and correlation coefficient.

Tracking- and Scintillation-Aware Channel Model for GEO Satellite to Land Mobile Terminals at Ku-Band

Recent advances in satellite to land mobile terminal services and technologies, which utilize high frequencies with directional antennas, have made the design of an appropriate model for land mobile satellite (LMS) channels a necessity. This paper presents LMS channel model at Ku-band with features that enhance accuracy, comprehensiveness, and reliability. The effect of satellite tracking loss at different mobile terminal speeds is considered for directional mobile antenna systems, a reliable tropospheric scintillation model for an LMS scenario at tropical and temperate regions is presented, and finally a new quality indicator module for different modulation and coding schemes is included. The proposedextended LMS channel (ELMSC)model is designed based on actual experimental measurements and can be applied to narrow- and wide-band signals at different regions and at different speeds and multichannel states. The proposed model exhibits lower root mean square error (RMSE) and significant performance observation compared with the conventional model in terms of the signal fluctuations, fade depth, signal-to-noise ratio (SNR), and quality indicators accompanied for several transmission schemes.

Modeling of the Land Mobile Satellite Channel considering the Terminal’s Driving Direction

A precise characterization of the Land Mobile Satellite (LMS) channel, that is, the channel between a satellite and a mobile terminal, is of crucial importance while designing a satellite-based communication system. State-of-the-art statistical LMS channel models offer the advantage of requiring only a few input parameters, which include the environment type and the elevation angle of the satellite. However, the azimuth angle relative to the driving direction of the mobile terminal is usually ignored, as its proper modeling requires either an extensive measurement campaign or a significant effort from the user, as a precise geometrical description of the scenario is required. In this contribution we show that the impact of the driving direction on the channel statistics is not negligible and requires to be modeled explicitly. Moreover, we propose a statistical LMS channel model whose parameters are obtained via an image-based state estimation method. The image-based method is verified by a comparison with measured radio frequency signal levels. The proposed method allows obtaining a complete statistical description of the channel for arbitrary elevation and azimuth angles.

A Three-Component Model Based on Macropropagation Phenomena Approach for Complex Building Scattering

Multipaths represent a common predominant and uncontrolled component on channel impairments for all terrestrial and Land Mobile Satellite systems. Without restrictions w.r.t mobile terrestrial applications, the addressed multipath problematic in this paper is focused on Land Mobile Satellite applications where delayed signal replicas are highly impacting performances on communication systems while they induce strong positioning errors for navigation systems. The actual trend in propagation channel modelling is to improve the multipath characterisation and representation by using semideterministic and hybrid physical-statistical models into channel simulators instead of narrow-band empirical approaches. In this context, this paper presents a new simplified model, called 3CM (3-Component Model) to reproduce building scattering in an efficient way which strongly improves computation performances. This model is based on asymptotic methods, namely, PO (Physical Optics) which allows the 3CM to be frequency scalable, polarimetric, and dielectric materials oriented. Note that the proposed model and the retained approach can be integrated into more complex tools such as existing ray tracers. However, this issue is not discussed in this paper.

Development of a MATLAB Toolbox for Mobile Radio Channel Simulators

A profound knowledge of mobile radio channels is required for the development, evaluation, and also assessment at practical conditions of present and future mobile radio communication systems. The modelling, analysis, and simulation of mobile radio channels are important key area in current context. In addition to that, knowledge of channel behaviour in mobile radio communication is extensively recommended for the study of transmitter/receiver performances under different propagation scenarios. Our intention in this research work was to develop various kinds of mobile fading channel simulators using MATLAB and embed them into MATLAB software as a toolbox. Implemented channel simulators were combined MATLAB as a toolbox which users can easily select well-known channel models to test and to study the performance of mobile communication systems. It gives better support for the new users to work on the developed channel simulators, run the test procedures as well as parameter computation. The toolbox contains channel simulators for simulating non-stationary land mobile satellite channel, spatial shadowing processes, MIMO channels, multiple uncorrelated Rayleigh fading channels, mobile to mobile channel, frequency hopping channels etc. Set of test procedures were developed such as the autocorrelation function ACF, average duration of fades ADF, the probability density function PDF, and the level-crossing rate LCR etc., in order to test and to confirm the correctness of the implemented channel simulators. Proposed new algorithms to compute the model parameters of the channel simulators were also implemented in the toolbox to enable the parameterization of the channel simulators under specific propagation conditions. Some of the simulation models were implemented based on specification of GSM system by CEPT-COST 207. DOI: http://dx.doi.org/10.4038/jur.v2i1-2.7853 J. Univ. Ruhuna 2014 2:40-45

Adaptive Long-Range Prediction of Three-State LMS Channel Model

In order to provide the accurate real-time knowledge of future channel state information for the adaptive transmission of narrowband land mobile satellite (LMS) communication systems, an adaptive long-range prediction (ALRP) method, suitable for a three-state LMS channel model at S-band, is proposed. The very slow shadowing conditions' variations of satellite propagation channel can be described as a three-state Gilbert---Elliot channel model based on Markov chain. The channel state of future long-range is predicted based on weighting prediction while the parameters of linear auto-regression model are updated using an iterative adaptive tracking algorithm. The future channel fading series are predicted by the latest observations within current channel state. Simulation results show that the proposed method can be used to predict the future long-range channel state and fading series of three-state Gilbert---Elliot channel model accurately; and it is observed from the mean square error results that the prediction performance of the ALRP method is much more accurate than that of long-range prediction method. Moreover, the method has advantage of real-time and low-complexity which will make the adaptive transmission techniques feasible for LMS channel models.

Radio Propagation Channel Measurements for Multi-Antenna Satellite Communication Systems: A Survey

For the terrestrial infrastructure, the multiple-input multiple-output (MIMO) architecture is a key technology that has brought the wireless gigabit vision closer to reality. Satellite communication systems have not been immune from this wave of innovation, and theoretical and experimental efforts have recently been devoted to the investigation of the applicability of multiple-antenna techniques to these systems. This paper intends to highlight and critically present the most important results from measurement campaigns conducted to characterize the radio channel of multi-antenna satellite systems. Emphasis is given on the viability of MIMO technology over satellite, and the potential enhancements in terms of channel capacity and link reliability that can be achieved through spatial and/or polarization diversity. The configurations under investigation range from very simple single-input multiple-output (SIMO) systems, with multiple antennas only at the terrestrial receiver, to quite complex and challenging systems, such as dual-satellite multiple-input single-output (MISO) systems, and single-satellite dual-polarized MIMO systems. The spotlight is on land mobile satellite (LMS) systems in outdoor radio propagation environments. However, satellite-to-indoor reception is also included.

Modeling of First-Order Statistics of the MIMO Dual Polarized Channel at 2 GHz for Land Mobile Satellite Systems Under Tree Shadowing

The Land Mobile Satellite (LMS) channel at 2 GHz is examined and the first order statistics are modeled using experimental data for two tree shadowing scenarios. Considering that the first order statistics of the channel are used as input to channel models as well as for the calculation of the system margins, the modeling of the probability density function (PDF) and the cumulative distribution function (CDF) of the received signal envelope is of great importance for the design of LMS systems. Experimental data from measurements performed in Prague, the Czech Republic, are presented for two scenarios, a Heavy Tree Shadowing one and an Intermediate Tree Shadowing one. Four of the most widely used distributions, Rayleigh, Rice, Loo and lognormal, are considered for the modeling of the CDF of the signal envelope. Loo and Rice distributions out of the four considered distributions provide the best fit with reference to the measured data. Moreover, analytical empirical expressions are given for the parameters of the Loo distributions as a function of the elevation angle, to be used for the modeling of the LMS channel under tree shadowing. It is found that the expressions for the estimation of the distributions' parameters provide a good fit to the experimental data.

Cooperative Hybrid Land Mobile Satellite–Terrestrial Broadcasting Systems: Outage Probability Evaluation and Accurate Simulation

Next generation communication networks incorporate Land Mobile Satellite (LMS) systems in order to provide greater areas of coverage and higher throughput for specific applications. Cooperation between satellite communication networks and terrestrial relays is or increasing the system's performance and availability. In this paper, the outage performance of a cooperative hybrid satellite and terrestrial system configuration is analytically evaluated assuming that the satellite links suffer from shadowed Rician fading, while the terrestrial link suffers from the Nakagami-m fading. Two cooperative relaying strategies are examined and the final formulas for the calculation of the outage probability are given. Moreover, a block diagram for the generation of time series for the reliable simulations of the outage probability of the cooperative hybrid land mobile satellite systems is given. The theoretical results and the simulation results almost coincide. Moreover, extended numerical results investigate the impact, of different shadowing conditions and more generally of the satellite links elevation angles, on the overall cooperative LMS system performance.

Modeling and Performance Evaluation of Dual Polarized MIMO Land Mobile Satellite Channels

paper is concerned with generating of narrow-band dual polarized Multi Input Multi Output (MIMO) over land Mobile Satellite (LMS) fading channels. In the absence of accurate experimental results of MIMO-LMS channels, a statistical model for the characterization of MIMO-LMS is proposed based on available experimental results for Single Input Single output (SISO) LMS and MIMO wireless channels as well as on their extrapolation to the MIMO-LMS case of interest. In this paper a step-by-step methodology for transforming SISO model (Loo model) to MIMO model with detailed description and block diagrams for the simulation and time series signal generation for MIMO-LMS, with the desired power, probability distribution, covariance relations and spectrum. Moreover, based on the proposed channel model, the channel capacity statistics as well as the error performance of MIMO- LMS are evaluated through computer simulation. Useful numerical results on the capacity are also provided taking into account several operational system parameters. The simulation model and results are useful for LMS-MIMO physical layer researches and system designer, who need an easy to implement and realizable model, representative of typical MIMO-LMS communication systems.

Enhanced spread Aloha physical layer design and performance

SUMMARYThis paper describes the key design and performance aspects of the Enhanced Spread Spectrum Aloha (E‐SSA) physical layer, which represents an essential component of the S‐band Mobile Interactive Multimedia European Telecommunication Institute standard. Thanks to advanced signal processing at the gateway side, the E‐SSA random access protocol allows to achieve unprecedented spectral efficiency in a pure asynchronous random access mode with high robustness against received packets power unbalance. The E‐SSA physical layer is closely derived from the Third Generation Partnership Wideband Code Division Multiple Access random access channel physical layer with some adaptation to best operate in the Land Mobile Satellite channels. Particular emphasis is devoted to the E‐SSA physical layer system design drivers as well to the packet transmission control policies, which are of high relevance for S‐band Mobile Interactive Multimedia. The demodulator architectural design is also illustrated jointly with some of the key detection performance. Finally, the E‐SSA random access protocol performance are reported for Additive White Gaussian Noise and satellite mobile channels. Copyright © 2014 John Wiley & Sons, Ltd.

Modeling and Performance Evaluation of dual polarized MIMO Land Mobile Satellite Channels

Modeling and Performance Evaluation of dual polarized MIMO Land Mobile Satellite Channels

Study of Vehicle Vibration for High-Performance Land Mobile Satellite Tracking System for Telemedicine

The land mobile satellite service (LMSS) is a key component of telemedicine and an important technology for grasping the status of a patient in an ambulance. However, rough road surfaces can destabilize satellite tracking and disturb data communications with the ambulance carrying the patient. Nevertheless, accurate estimates of the location of the vehicle at any given time and rapid reconfiguration of the tracking antenna based on past data can allow stable and effective data communications. This study examined positions characterized by large vibration amplitudes from past data on vehicle vibrations due to rough road surfaces as feature points to provide the vehicle system in advance with reference pitch angle vibration data. Drawing on reference vibration data for convolution and a cost function, The authors synchronized past data with real-time vibration data and accurately estimated the point at which the ambulance or other vehicle passes on the road. They also discuss limits on the range of vibrations that can be used for data synchronization. This study demonstrates that the present method enables high-precision estimates of vehicle location.

Performance Evalutaion of Land Mobile Satellite System over Lutz Fading Channel for BPSK Modulation Scheme

In this paper, different statistical models of land mobile satellite channel are studied with emphasis on Lutz Model. The reason for selecting Lutz Model is that this model shows best distribution in the entire environment (open area, semi shadowed and shadowed region). The Lutz Channel Model is simulated in Matlab using random number generator technique and is validated. The channel model is used to evaluate the performance of satellite system in terms of Bit error rate using BPSK modulation scheme and is compared with AWGN, Rician and Rayleigh channel.